An unexpected journey into geochemistry
- Wits Chemistry
Wits student Kei Prior shares the story of his journey as an undergraduate considering Chemical Engineering to a PhD in Geochemistry and Environmental Science.
Kei Prior has been awarded a scholarship to pursue a PhD at Macquarie University in Sydney, Australia. Kei will work under the supervision of Dr Tim Ralph and Prof Marc Humphries to investigate the impact of fire and floods in New South Wales, and the role of floodplain wetlands in buffering coastal systems. Kei completed his Honours degree in chemistry in 2024, winning the Merck Achievement Award as the top student. Read about his journey here.
As a second-year BSc Chemistry student with plans to shift to Chemical Engineering, I never anticipated that a field trip to Lake Bhangazi North in the iSimangaliso Wetland Park would completely change my academic trajectory. When I arrived at the ORI research cottage—a modest setup of four shipping containers arranged around a makeshift living room - I had little idea what a sediment core was, and terms like bathymetry were foreign to me.
I joined the research team through my analytical chemistry lecturer, Prof. Marc Humphries (WITS), who, alongside Prof. Andrew Green (UKZN), had chosen Lake Bhangazi as part of their broader paleoclimate and geophysical research in the region. Their previous work had focused on the Mkhuze Delta and Lake St. Lucia, but Lake Bhangazi offered an unstudied site to expand their understanding of past environmental changes in northern KwaZulu-Natal.
Our field expedition involved several days of manual sediment coring, constructing a makeshift seismic survey system on a small rubber duck, and many braais and fireside conversations. It was in these informal settings that I learned the most, connecting lessons from the professors to what I was seeing at the lake and have seen in the natural spaces in South Africa. I was able to ask questions that pushed my understanding beyond the classroom and the laboratory.
Although I had assisted with subsampling the core in my third year and we had already received our age model, it wasn’t until my Honours year that I fully took ownership of the project. In the lab, I worked on grain size analysis to assess sediment deposition patterns, XRF analysis to identify elemental composition shifts, and I even worked in the ultra-clean laboratory at Wits to investigate 87Sr/86Sr and 143Nd/144Nd ratios as tracers of sediment provenance. One of our most striking findings was the presence of prominent sand lenses throughout the core, confirmed through grain size and elemental data We attributed these lenses to prolonged drought periods, during which reduced vegetation cover and lower moisture availability would increase sediment erodibility. Our findings aligned with Prof. Humphries' previous research, which linked intensified drought cycles to harsh El Niño phases in the region.
To strengthen our conclusions, we combined data from three core sites—Lake Bhangazi, the Mkhuze Delta, and Lake St. Lucia—into a multi-proxy composite record. The results showed a statistically significant correlation between major periods of drought in KZN and a longstanding El Niño proxy record from Ecuador. The results of this work were recently published in Quaternary Science Reviews: A 6000-year high-resolution composite record of El Niño-related drought in subtropical southeast Africa.
The experience altered my academic direction. Instead of pursuing chemical engineering or chemistry, I have decided to continue my research in earth sciences and have accepted an offer for a PhD at Macquarie University, under the supervision of Dr Tim Ralph and Prof Humphries. My PhD will expand on my interest in extreme climate events, specifically investigating how the Black Summer fires have impacted coastal wetlands in New South Wales. Focusing on freshwater wetlands upstream of coastal mangroves, I aim to conduct source-to-sink geochemical analyses to track sediment transport post-fire and to develop expertise in radioisotope and compound-specific isotope analysis as well as geochemical modelling and remote sensing.
Although I never set out to pursue a PhD in Geochemistry and Environmental Science, I am incredibly grateful to have landed here. The field offers a rare opportunity to blend my deep curiosity for the natural world with my fundamental understanding of chemistry, as I intend to embrace an interdisciplinary approach to addressing climate and environmental challenges.